A new book argues that most medical mistakes are the result not of technical mishaps but of common mental traps. Here are four things to watch out for

The patient was an 8-year-old California girl with severe headaches. Her parents, who were both struggling to adjust to new high-pressure jobs, took her to top neurologists and pediatricians. The child's symptoms, the doctors concluded, were a response to stress at home, along with perhaps a sinus condition. But four or five months later, it became clear that she had a brain tumor and needed surgery. When her doctors looked back at early scans of her brain, they were aghast to see the shadow of a tumor they had previously overlooked.